Definition

A reference is an alias for another variable

• Alias: another name that is bound to the aliased variable
  • Mutating a reference is mutating the aliased variable
• Introduced in C++ as part of the language

Pass-By-Reference

C++ allows you to use real pass-by-reference

• Client passes in an argument with normal syntax
  • Function uses reference parameters with normal syntax
  • Modifying a reference parameter modifies the caller’s argument

Example

Declare Reference

int main(int argc, char** argv) {
	int x = 5, y = 10;
	int& z = x; // binds the name "z" to x

	z += 1; // sets z (and x) to 6
	x += 1; // sets x (and z) to 7

	z = y;  // sets z (and x) to the value of y
	z += 1; // sets z (and x) to 11
	return EXIT_SUCCESS;
}

Pass By Reference

void swap(int& x, int& y) {
	int tmp = x;
	x = y;
	y = tmp;
}
int main(int argc, char** argv) {
	int a = 5, b = 10;
	swap(a, b);
	cout << "a: " << a << "; b: " << b << endl; // a and b are swapped
	return EXIT_SUCCESS;
}

Memory Diagram